Effect of argon plasma-treated polyethylene terepthalate on ZnO:Al properties for flexible thin film silicon solar cells applications

The 0.4 μm-thick Aluminum-doped Zinc Oxide (ZnO:Al) films were deposited at 100°C on polyethylene terephthalate (PET) substrates by Radio Frequency (RF) magnetron sputtering. Prior to the AZO deposition, an Argon plasma treatment on the substrate surface was carried out by applying a RF bias power on it without intentional heating. The parameters varied in the etching process were the plasma etching time from 0 to 360 s, the RF bias power from 50 to 250W, and the gas flux from 3 to 5 sccm. The effect of the substrate surface treatment on the mechanical stability, crystallinity and the optoelectronic properties of ZnO:Al thin films were evaluated. The results showed physically stable ZnO:Al films with good adherence to the substrate using appropriated plasma treatment parameters. This fact was attributed to physico/chemical PET surface modifications on the first few molecular layers after the plasma irradiation. The performance of flexible solar devices fabricated on optimized ZnO:Al thin films with adequate adhesion and optoelectronic properties was analysed.